Apparatus for making piston rings



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19 Fil v ed Jun e 16 A F I P c 1943 PARAT W. W

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April 19, 1949. F. w. WILKENING APPARATUS FOR MAKING PISTON RINGS 2 Sheets-Sheell 2 Filed June 16, 1943 A190134@ WW2@ Patented Apr. 19, 1949 APPARATUS FOR MAKING PISTON RINGS Frederick W. Wilkening, Narberth, Pa., assignor to Wilkening Manufacturing Company, Philadelphia, Pa., a corporation of Delaware Application June 16, 1943, Serial No. 490,964

4 Claims.

The present invention relates to. certain new and useful piston rings, and it relates more particularly to a certain new and useful method of and apparatus for making trans-split annular piston rings of a type generally adapted for use in internal combustion engines or the like.y

An object of the present invention is to provide a method of and apparatus for making piston rings, whereby the "piston rings are adapted to provide a truer and more accurate t within a cylinder. Another object of the present invention is to provide a method of and apparatus for forming piston rings which have relatively uniform plus-circularity and which, at the same time, are light-tight, throughout their circumference and give a good pressure pattern,

Other objects and advantages of the present invention are apparent in the following detailed description, appended claims, and accompanying drawings.

In making piston rings of the trans-split annular type, it has been found important that the rings have relatively uniform outward tension throughout their circumference, and that the rings, when coniined in a, cylinder, conformaccurately to the inner wall of the cylinder. To

attain these properties, trans-split, annular piston rings should be constructed with uniform inherent tension and with a slight plus-circu- 1arity; plus-circularity being defined as a slightly greater diameter across the gaps of the piston ring than the diameter measured at 90 degrees to the gaps when the ring is confined in a flexible annulus of cylinder size. This plus-circularity should range from 0.010 to 0.025 inch; it being important, however, that variation in plus-circularity be held to a minimum.

In the past, .it has been the practice to obtain this plus-circularity by turning the piston ring. However, this method is undesirable since the plus-circularity attained varies all the Way from zero to 0.039 inch and more, and furthermore, this conventional method gives a poor pressure pattern and creates a tendency in the ring toward not being light-tight at points approximately one inch on either side of the gap.

' According to the present invention, it is possible to produce rings which are generally uniform in plus-circularity (the variation in plus-circularit-y being held to approximately 0.010) and which, at the same time, give a good pressure pattern and are generally light-tight throughout their circumference.

(ci. zes-2) Another phase of the present invention consioning operation 'or treatment and that the plus- 'circularity treatment of the present invention is applicable to any trans-splitpiston ring regardd less of how tension is imparted to it.

For the purpose of illustrating the invention, there is shown in the accompanying drawings one form thereof which is at present preferred, since the same has been found in lpractice to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangements and organizations of the\ instrumentalities asv herein shown and described.

Referring to the drawings, in which like reference characters indicate like parts throughout,'

Figure 1 represents a perspective view of one embodiment of the present invention, in assem- Figure 5 represents a view generally similar to that of Figure 4, but showing the appearance of the end piston ring after the assembly has been tightened, to give the plus-circularity.

Figure 6 represents a perspective view of a spider which is used for immersing the assembly of Figure 1 in a heat-treating bath.

Figure '7 represents a side-elevational view of a stack of trans-split piston rings, as they appear when assembled on the embodiment of Figure 1, and immersed in a heating bath upon the spider of Figure 6.

Figure 8 represents a fragmentary end elevational view on an enlarged scale showing a modified embodiment in `which the pressure edges 26-a are made slightly concave.

For purposes of illustration, there is shown in the drawings one form of apparatus which may.

be employed in imparting both plus-circularity and tension to a plurality of piston rings in a single heat-shaping operation. However, as stated above, the present invention is directed primarily to the plus-circularity treatment and is wholly independent of any heat-tensioning operation. It is, therefore, .to be understood that my novel method of imparting plus-circularity to trans-split piston rings can be practiced with the aid of many other types of apparatus; the

illustrated apparatus being purely illustrative and not restrictive.

In brief, my novel method of imparting pluscircularity to a trans-split piston ring comprises the application of outward, generally radial, distending pressure to the free ends of the ring, the provision of external support for the ring at two points upon the outer periphery of the ring spaced equidistant and substantially removed from the free ends (the remainder of the ring being left wholly unrestrained), and the heat-setting of the ring in its so-distended condition.

The application of the outward, generally radial, distending pressure upon the free ends of the ring coupled with the external support at two points upon the outer periphery of the ring, spaced equidistant and substantially removed from the free ends, increases the radius of curvature of a substantial portion of the ring adjacent the free ends while leaving the radius of curvature of the greater portion of the ring substantially unaffected. The points of external support lie within the half of the periphery adjacent the free ends so that the above-described increase in radius of curvature increases the diameter of the ring measured across the gap over the diameter measured at right angles thereto and thus results in plus-circularity as defined above. The heat-setting fixes the ring in this condition.

My method of imparting plus-circularity to a trans-split piston ring may be em'ployed simul- Itaneously with a heat-tensioning operation as will be described in detail hereinbelow. My method may also be employed equally well upon a piston ring which has been pre-tensioned in any conventional way whatever. My method may, furthermore, be employed upon an untensioned ring to impart only plus-circularity there.-4

to; it being possible subsequently to treat the ring to impart tension to it by any conventional method. Y

One embodiment of the apparatus intended primai-.ily for imparting both plus-circularity and f tension in a single operation is shown in Figures 1 to 5 of the drawings, and is made up of three main parts, namely, a tension bar 20, a cam fixture 2|, and a circularity bar or spacer bar 22.

The tension bar 20 is an elongated bar of metal or the like, which may have a generally wishbone cross-section.

An expander portion 23 is formed on the underside of the tension bar 20. The expander portion 23 has a predetermined transverse dimension, so that, when the ends of the trans-split piston rings are spread apart thereby, the desired amount of tension will be imparted 4to the rings.

A`pair of inclined shoulders 24 are formed on the back or bottom side of the tension bar 20 on either side of the expander portion 23 thereof.

A plurality (as, for example, 3) of internally screw-threaded openings 25 extend upwardly through the center of the tension bar 23.

The cam fix-ture 2| is preferably of heat-resistant metal such as nichrome which retains its shape and proportions during heating and which does not scale. The cam fixture 2| is an elongated member which may be of generally U-shaped cross-section having inclined pressure edges 23 formed along the upper ends of' the arms 21 thereof. The pressure edges 23 may be formed as plane bevels or chamfers.

A plurality (as, for example, 3) of openings 23 are formed in the base of the cam fixture 2|, generally in line with the screw-threaded openings 25 in the tension bar 20. The cam fixture 2| may be perforated, as at 23, to permit circulation of liquid therethrough` in the heating bath to be hereinafter described.

A plurality of strengthening ribs 30 may also be provided on the outer side of the cam fixture 2| The circularity bar or spacer bar 22 is a simple fiat piece of steel or the like, which has a length generally the same as that of the cam fixture 2| and the tension bar 2li,l The circularity bar or spacer bar 22 is provided with a plurality (as, for example, 3l of openings 3|, generally matching with the openings in the tension bar 20 and the cam fixture 2l. The circularity bar or spacer bar 22 has a predetermined thickness, to give the desired plus-circularity, as will be hereinafter described.

A plurality (as, for example, 3) of externally screw-threaded vbolts 32 are adapted to pass through the openings 23 in the cam fixture 2| and the openings 3| in the circularity bar 22, and to engage in the screw-threaded openings 25 in the tension bar 20. As can be seen particularly in Figures 2 and 5, the tightening of the bolts 32 will pull the tension bar, the circularity bar, and the cam fixture into rigid aligned relationship with the circularity bar 22 intermediate the tension bar .20 and the cam fixture 2|. It can also be seen that the spatial relationship between the shoulders 24 of the tension bar 20, and the pressure edges 26 of the cam fixture 2| is dependent upon the thickness of the circularity bar 22; the thicker the circularity bar 22, the closer the shoulders 24 are to the pressure edges 23 and vice versa.

In practicing the present invention, a plurality of trans-split annular piston rings 33 are first assembled on the tension bar 20, as shown in Figure 3, with the free ends 34 of the piston rings spread tangentially apart by the expander portion 23 of the tension bar 23. As previously stated, the transverse dimension of the expander -portion 23 is so adjusted that, when the `piston rings 33 are assembled thereon, as in Figure 2 and Figure 3, the desired tension or pressure ls created in the rings. That is, depending upon the size of the ring, and the character of use to which it is to be put, the transverse dimension ofthe spacer portion 23 of the tension bar 23 is made larger or smaller. i

The tension bar 23 with its associated piston rings 33`is then connectedto the circularity bar 22 and the cam fixture 2|, by inserting and partially tightening the bolts 32. The partially tightened assembly isshown in Figure 4, wherein it can be seen that, while the shoulders 24 of the .tensionbar 20 contact the inner periphery of the piston rings 33 adjacent the ends 34 thereof, and while the pressure edges 23 of the arms 21 of the cam fixture 2| contact the outer periphery of the piston rings 33 at a point 1/2 or 2 inches on either side of the free ends 34, neither the shoulders 24 nor the pressure edges 26 exert any appreciable pressure upon the piston rings 33; the piston rings 33 being in generally the same condition in Figure 4 as in Figure 3.

When, however, the bolts 32 are further tightened, as in Figure 5, the freel ends 34 of the piston rings 33 are pulled downwardly by the shoulders 24 of the tension bar 20, while the pressure edges 26 of the cam fixture 2| provide external support for the outer periphery of the piston rings 33 at points removed approximately one-quarter of the circumference of the rings and equidistant from the free ends 34. That is, each of the pressure edges -28 provides support at a point more or less approximately one-eighth of the circumference from the adjacent end 31.

It is apparent that this final tightening of the bolts 32 forces the free ends 34 of the piston rings radially outwardly, to give plus-circularity. It is apparent also that the degree to which the ends 34 are forced outwardly is dependent upon the thickness of the circularity bar or spacer bar 22. That is, if a relatively thick circularity bar or spacer bar is employed. the ends 34 of the piston rings 33 will be forced outwardly relatively slightly, so that the ring will have only a relatively slight plus-circularity. If, on the other hand, the circularity bar 22 has a relatively small thickness, the ends 34 of the-piston rings 33 will be forced outwardly'a comparatively larger distance, to correspondingly increase the plus-circularity of the rings. By using circularity bars or spacer bars of different thicknesses, different-size rings can be given plus-circularity on the same tension bar and cam fixture.

When the assembly is in its final tightened position, it can be seen that the rings are supported in position only at their free ends 34 and at the points of contact with the pressure edges 26; the remainder of the rings being free and unrestrained. The rings, in this position, have a stress induced in them due to the spreading apart of,

their' ends by the expander portion 23 of the tension bar 20, and also the outward stress induced by the action of the shoulders 24 and the pressure edges 26.

A spider 35, having a central rod 36 extending therefrom is employed to immerse the assembled unit into and to remove it from a heating bath 3l. As shown in Figure 7, one end of the assembled unit is seated upon the spider 35, so that the unit is vertically disposed, with the rod 36 passing upwardly intermediate the piston rings 33. A removable handle 38, adapted to be connected within a hole 39 in the free end of the rod 36, is employed to lower and raise the spider into and from the bath 31.

The heating bath containing any suitable heating fluid is then raised to a temperature of begiven plus-circularity by- `other methods) to bel not light-tight at points approximately one inch'- tween 1150 and 1200 F., at which temperature.

a normalizing takes place, which re-sets the n'iolecules in the piston rings in the new positions, and,

thereby, produces both tension and plus-circularity in the piston rings, in the same operation. Due to the inclination of the shoulders 24 and the pressure edges 25, the apparatus of the present invention is designed tolaccommodate a range of different-size piston rings.

While the novel method and apparatus of the present invention are intended primarily for the ltreatment of cast-iron piston rings, they can be used equally well in the treatment of steel piston rings, as well as piston rings of other materials.

While, for purposes of illustration, the piston rings 33 shown in the drawings, are so-called compression rings of the imperforate type, the

4novel method and apparatus of the present invention are adapted equally well for treatment of the so-calle'd oil-control rings of slotted or otherv similar type.

Due to the fact that the distance between the ends of the rings andthe pressure edges of the `cam fixture is of suiiicient length (totaling approximately one-fourth the circumference), a

" good pressure pattern is obtained, and the ring one-eighth the circumference).

Since the rest of the circumference of the ring (namely three-fourths thereof) remains unrestrained during the heat-setting operation, the pressure pattern of the entire ring is exceptionally good. f

either side of the free ends of the rings (less than Where the apparatus of the present invention is intended for use only on a single size of ring, the circularity bar or spacer barcan be omitted and the dimensions of the tension bar and the cam fixture can be so proportiora'd as to give the desired degree of plus-circularity, when the tension bar is tightened directly against the cam fixture (without the intervening spacer bar) This can be done by merely increasing the depth or thickness of the expander portion of the tension bar to compensate for the thickness of the removed spacer bar.

Instead of using interchangeable spacer bars of different thicknesses to accommodate differentsize rings, it is possible to use interchangeable tension bars having expander portions of different thicknesses.

It can be seen that the novel method and apparatus of the present invention effect an increase in the radius of curvature of approximately one-fourth of the piston ring while leaving the remaining more or less approximately threefourths substantially unchanged. That is, when a piston ring is made according to the present invention, the radius of curvature thereof is increased throughout approximately one-eighth its circumference on either side -of the gap or split,

While its radius of curvature throughout theremaining approximately three-fourths of its circumference remains substantially unchanged. It is apparent that this increase in the radius of curvature of the portion adjacent to the gap or split results in plus-circularity as defined hereinabove.

Since the radius of curvature of a substantial portion of the piston ring adjacent the gap or split is increased, only a very slight increase in the radius cf curvature is required to produce tl-.e desired plus-circularity. Thus, the shape and tension of the ring remain relatively uniform and the ring retains a good pressure pattern and also remains substantially light-tight throughout its periphery.

While I prefer to effect the change in radius .of curvature of approximately one-fourth of the circumference of the ring (adjacent the gap or split), the present invention is not so limited and contemplates such increase in radius of curvature throughout any substantial portions of the circumference up to one-half of the circumference.

In Figure 8 there is shown a modified embodiment of the present invention which employs slightly rounded concave p-ressure edges 26- a in place of the plane pressure edges 26 shown in Figures 4 and 5. The pressure edges 2li-a have a greater radius of curvature than that of the piston rings 33. The rounded concave pressure edges 2li-a may, in some instances, be preferred since they afford a somewhat greater line of contact intermediate the pressure edges and the piston rings and thus provide a more gradual transltion between the lowermost distended portions of the rings and the upper unchanged portions thereof, thereby to give an even better pressure pattern in the final rings.

As stated hereinabove, the present invention` 7 also contemplates the plus-circularity treatment of piston rings which have been previously given tension by any conventional method.

That is, the plus-circularity treatment of the present invention can also be applied to a piston ring `which has previously been treated by any conventional 4method so that the free ends are already permanently substantially spread `apart when the rings is unconned.

When rings so pre-tensioned are treated ac cording to the present invention, the portion 23 of the bar does not operate as an expander portion since the free ends 34 of the rings are already normally spread apart a distance corresponding generally to the transverse dimension of the portion 23; said portion 23 serving merely to support the ends 3l against displacement or movement relative to each other during the distending thereof (upon tightening of the bolts 32) and during the subsequent heat-setting operation.

As also stated hereinabove, the present invention also contemplates the plus-circularity" treatment of untensioned rings; that is, rings which, when unconned, have their free ends close together with little or no gap therebetween.

When it is desired to impart only plus-circularity to an untensioned ring (without also simultaneously imparting tension thereto), the transverse dimension of the portion 23 of the bar 20 may be reduced to a point at which the portion 23 will no longer impart tension to the ring when the ends 34 of the ring are seated against it; the portion 23 in such case serving merely to support the ends 34 against displacement or relative movement during the distending and heat-setting operations, instead of serving as an expander portion. Where it is not desiredV simultaneously to heat-tension the ring, the portion 23 of the bar 20 may. indeed, be omitted entirely.

The present invention may be embodied in other specic forms with departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.`

Having thus described the invention, what I claim as new and desire to protect by Letters Patent, is:

1. A clamp for use in imparting plus-circularity to trans-split annular piston rings comprising an elongated bar having a portion adapted to support the free ends of a plurality of axially contiguous rings against relative movement thereof and having shoulders adapted to contact the inner peripheriesof said rings adjacent the free ends thereof, an elongated cam fixture having pressure edges adapted to contact the outer peripheries of said rings at points equidistant and substantially spaced apart from said free ends, and adjustable means connecting said elongated bar and said cam fixture and adapted to apply pressure to said rings through said shoulders and to provide external support for said rings V-atsaid pressure edges.

2. A clamp for use in imparting plus-circularity to trans-split annular piston rings compris- 8 ferentially spaced relationship and having shoulders adapted to contact the inner peripheries of said rings adjacent the free ends thereof, an elongated cam fixture having pressure edges adapted to contact the outer peripheriesof said rings at points equidistant andsubstantially spaced apart from said free ends, an elongated separator bar of predetermined thickness disposed intermediate said tension bar and said cam fixture, and adjustable means connecting said tension bar and said cam fixture and adapted to apply predetermined pressure to said rings through said shoulders and to provide external support for said rings at said pressure edges.

3. A clamp for use in imparting plus-circularity to trans-split annular piston rings comprising an elongated bar havinga portion adapted to support the free ends of a plurality of axially contiguous rings against relative movement thereof and having shoulders adapted to contact the inner peripheries of said rings adjacent the free ends thereof, an elongated cam fixture having elongated generally plane kbeveled pressure edges adapted to contact the outer peripheries of said rings at points equidistant and substantially rspaced apart from said free ends, and adjustable means connecting said'elongated bar and said cam fixture and adapted to apply pressure to said rings through said shoulders and to provide external'support for said rings at pressure edges.

4. A clamp for use in imparting plus-circularity to trans-split annular piston rings comprising an elongated bar having a portion adapted tc support the free ends of a plurality of axially contiguous rings against relative movement thereof and having shoulders adapted to contact the inner peripheries of said rings adjacent the free ends thereof, an elongated cam fixture having elongated pressure edges adapted to contact the cuter 40 peripheries of said rings at points equidistant REFERENCES CITED The lfollowing references are of record in the ille of this patent:

ing an elongated-tension bar having a portion adapted to support the free ends of a plurality of axiallycontiguous rings in predetermined circum- UNITED STATES PATENTS Number Name Date 1,051,752 Noyes Jan. 28, 1913 v1,283,138 Frank Oct. 29, 1918 1,321,539 Mummert Nov. 11, 1919 1,380,136 Doan May 31, 1921 1,458,248 Seifert Jan. 12, 1323 1,758,575 Marshall May 13, 1930 1,879,078 Carlsen Sept. 27, 1932 1,894,590 Ingersoll Jan. 17, 1933 1,964,156 Hoern June 28, 1934 2,033,093 Covert Mar. 3, 1938 2,093,263 Wuerfel Sept. 14, 1937 2,222,922 Wallace Nov. 28, 1940 2,280,552 Somes Apr. 21, 1942 FOREIGN PATENTS Number Country Date Great Britain Nov. 11, 1935 

